Silver alloy



Patented May 17, 1927.

UNITED STATES PATENT OFFICE.

ROBERT H. LEAiCH, OF BRIDGEPOBT, CONNECTICUT, ASSIGNOB TO HANDY 8aKABMEN,

A CORPORATION OI NEW YORK.

SILVER ALLOY.

Io Drawing.

This invention relates to an improvement in silver alloys, and theobject of the inven tion is to provide a silver which has reatresistance to tarnishing or other disco oration, or more specificallythe object em braces an alloy containing a preponderating amount ofsilver and also containing cadmium and antimony.

This alloy is to be made preferably of sterling fineness, and the termsterling is used to'designate a silver alloy which contains, perthousand parts, approximately 925 parts of silver and 75 parts of basemetal, which is usually copper. Such silver is subject to discolorationand this may result either by reason of various substances contained indilute form in the atmosphere, or, in the case of table ware, thediscoloration or tarnish may result from the exposure of the metal tothe action of fruit acids, foods containing sulphur in various forms,and other substances which contain elements which act on the silver.

As has reviously been stated, it is the object of tliis invention toprovide a silver, preferably of sterling quality, which resistsdiscoloration, and I accomplish this result by substituting for thecopper ordinarily used in such an alloy, cadmium and antimony. Such analloy not only resists tarnishing but by the proper selection oi theproportions of these metals an alloy may be roduced which has varyingmechanical qua ities.

It has been found that when cadmium is added to silver there is produceda very ductile white alloy which can be worked by rolling, spinning, andthe like, to a greater extent than the standard silver-copper alloy,without becoming hard. The cadmium appears to form a homogeneous alloywhich is of uniform quality and which is satisfactory in many respectsas, for instance, having tarnish resisting properties, but such an alloyis usually so soft that an article made from it, provided little work isdone on the metal during the manufacture, will be comparatively soft andwill not offer sufiicient resistance to ordinary use. Such an articlewill, therefore, become dented or bent readily, and is objectionable forthat reason.

On the other hand, the addition of antimon to a silver alloy increasesthe resistance of t e metal to tarnish, and in addition makes it quitebrittle and difficult to work.

Serial No. 659,394.

However, by combining the three ingredients above mentioned, namely,silver, antimony and cadmium, in proper proportions, it is possible tosecure an alloy which has the desired tarnish-resisting qualities andwhich has the ductility, and malleability which ma be required for anyparticular use.

11 alloy which fulfills the above requirements will contain apreponderating amount of silver, for instance, about 92.5%, when thealloy is to be of sterling fineness, and an amount of cadmium varyingbetween 1% and 7%, and antimony between (3.5% and 0.5%. An alloy inwhich the cadmium approaches the upper limit will be comparatively softand ductile, and will be used for the production of articles in whichconsiderable working of the metal is required, while where littleworking is carried on during the manufacture, the alloy will containcadmium approaching the lower limit. For what may be called ageneral'purpose alloy, the proportions will be approximately 2.5% ofcadmium and 5% of antimony, the remainder of the alloy being made up of92.5% of silver, when the alloy is to be of sterling quality.

From a scientific viewpoint a silver alloy which is designated as solidmay contain as low as 66 of silver, the remainder being made up ofvarious base metals with copper usually employed heretofore.

Silver which is used for manufacturing purposes may also run as high as95% pure silver, in which event it is, of course, liner than sterling.That silver which is in greatest demand is sterling silver, and I havepreviously described the proportions of the ingredients which will bepresent in my non-tarnishing alloy of that fineness, but it is to beunderstood that by following the principles of the invention here setforth, it is possible to make alloys of other than sterling finenesswhich will have qualities which will be required by the purposes towhich the alloy'is to be put. As I have stated, cadmium with silverproduces a ductile alloy which has tarnish-resisting properties, butthis alloy is so soft that unless some hardening ingredient is employedan article made from such a combination would be easily dented and bent.Accordingly, antimony is employed and the addition of the antimony makesit possible to control the malleability and ductility. The amount ofantimony which will be included will naturally be selected in accordancewith the purpose to which the alloy is to be put, but it may he said, ingeneral, that the cadmium present will rangeifrom about 13% to about 93%of the combined amount of cadmium and antimony present, while theantimony will consequently range from about 87% to about 7% of thiscombined amount. The skilled metallurgist will be able to determinewithout difliculty the amount of antimony which is to be included inorder to secure a metal of the desired mechanical qualities.

In producing such an alloy various methods may be used, but oneconvenient method consists in first making up an alloy of silver andcadmium which contains approximately 60% of silver and of cadmium. Thecadmium is first melted in a reducing atmosphere under a heavy)rotective cover such as charcoal, then the si ver separately melted andpreferably under a cover, is'added thereto and the two metals thoroughlymixed. A sample of this mixture which is found to be ver homogeneous, istaken and analyzed and on the basis of this analysis there is computedthe necessar amount of fine silver and antimony whic is required to makethe final mixture. The silver which is to be added is then melted andafter it is thoroughly liquid the required amount of antimony is addedthereto to form a silverantimony mixture. To this molten mixture the proor weight of the silver-cadmium alloy 1s a ded, and with this method themetals are found to be mingled in the final product in a uniform manner.These several melting and mixing steps should be carried on in areducing atmosphere to secure the best results.

While the above process is entirely satisfactory I do not desire tolimit myself to this exact rocedure. In any process, however, for tieproduction of this alloy, care should be taken in the manner in whichthe cadmium is added, inasmuch as it is readily oxidized at thetemperature at which the melting is carried on.

An alloy containing the ingredients above referred to is found to resistcorrosion or discoloration to a much greater extent than is the casewith ordinary alloys containing copper as the base metal. The new alloy,aside from its non-tarnishing qualities, may he made with varyingmechanical properties such as hardness, brittleness, and the like, b theproper selection of the amounts of ca mium and antimony used. Theantimony combined with the silver not only serves to give the silver atarnish-resisting quality but also serves to harden the alloy. In viewof the properties possessed by the new alloy, it will be apparent thatit is capable of wide use in the production of various metallic articlesand is desirable for the manufacture of table ware or hollow ware.

I claim:

1. An alloy containing a preponderating amount of silver and about 7.5%of cadmium and antimony, the cadmium ranging from about 1% to 7% and theantimony from about 6.5% to 0.5%.

2. An alloy containing about 92.5% of silver and about 7.5% of cadmiumand antimony, the cadmium rangin from about 1% to 7%, and the antimony rto 0.5%.

3. An alloy containing about 925 parts of silver, about 50 parts ofantimony, and about 25 parts of cadmium.

In testimony whereof I aflix my signature.

ROBERT H. LEACH.

om about 6.5%

antimony which will be included will naturally be selected in accordancewith the purpose to which the alloy is to be put, but it may be said, ingeneral, that the cadmium present will range from about 13% to about 93%of the combined amount of cadmium and antimony present, while theantimony will consequently range from about 87% to about 7% of thiscombined amount. The skilled metallurgist will be able to determinewithout difliculty the amount of antimony which is to be included inorder to secure a metal of the desired mechanical qualities.

In producing such an alloy various methods may be used, but oneconvenient method consists in first making up an alloy of silver andcadmium which contains approximately 60% of silver and of cadmium. Thecadmium is first melted in a reducing atmosphere under a heavyprotective cover such as charcoal, then the silver separately melted andpreferably under a cover, isadded thereto and the two metals thoroughlymixed. A sample of this mixture which is found to be ver homogeneous, istaken and analyzed an on the basis of this analysis there is computedthe necessary amount of line silver and antimony which is required tomake the final mixture. The silver which is to be added is then meltedand after it is thoroughly liquid the required amount of antimony isadded thereto to form a silverantimony mixture. To this molten mixturethe proper weight of the silver-cadmium alloy is added, and with thismethod the metals are found to be mingled in the final product in auniform manner. These several melting and mixing steps should be carriedon in a reducing atmosphere to secure the best results.

While the above process is entirely satisfactory I do not desire tolimit myself to this exact procedure. In any process, however, for theproduction of this alloy, care should be taken in the manner in whichthe cadmium is added, inasmuch as it is readily oxidized at thetemperature at which the melting is carried on.

An alloy containing the ingredients above referred to is found to resistcorrosion or discoloration to a much greater extent than is the casewith ordinary alloys containing copper as the base metal. The new alloy,aside from its non-tarnishing qualities, may he made with varyingmechanical properties such as hardness, brittleness, and the like, b theproper selection of the amounts of ca mium and antimony used. Theantimony combined with the silver not only serves to give the silver atarnish-resisting quality but also serves to harden the alloy. In viewof the properties possessed by the new alloy, it will be apparent thatit is capable of wide use in the production of various metallic articlesand is desirable for the manufacture of table ware or hollow ware.

I claim:

1. An alloy containing a preponderating amount of silver and about 7.5%of cadmium and antimony, the cadmium ranging from about 2, to 7% and theantimony from about 6.5% to 0.5%.

2. An alloy containing about 92.5% of silver and about 7.5% of cadmiumand antimony, the cadmium ranging from about 1% to 7%, and the antimonyfrom about 6.5%-

3. An alloy containing about 925 parts of silver, about 50 parts ofantimony, and about 25 parts of cadmium.

In testimony whereof I aflix my signature.

ROBERT H. LEACH.

CERTIFICATE OF CORRECTION.

Patent No. 1,628,673.

Granted May 17, 1927, to

ROBERT H. LEACH.

lt is hereby certified that the name of the second mentioned assignee inthe above numbered patent was erroneously written and printed as"Harmon" where" said name should have been written and printed as"Harman", as shown by the records of assignments in this office; andthat the said Letters Patent should be read with this correction thereinthat the same may conform to the record of the case in the PatentOffice.

Signed and sealed this 7th day of June, A. D. 1927.

Sea]

M. J. Moore, 7 Acting Commissioner of Pateuto.

CERTIFICATE OF CORRECTION.

Patent No. 1,628,673. Granted May 17, 1927, to

ROBERT H. LEACH.

It is hereby certified that the name of the second mentioned assignee inthe above numbered patent was erroneously written and printed as"Harmen" where" said name shouid have been written and printed as"Harman", as shown by the records of assignments in this office; andthat the said Letters Patent should be read with this correction thereinthat the same may conform to the record of the case in the PatentOffice.

Signed and sealed this 7th day of June, A. D. 1927.

M. J. Moore, Seal. Acting Commissioner of Patents.

